What is Occupational Contact Dermatitis? An Operational Definition

Multiyear Group and Medical Center Patch Test Frequency Data: Confounding Variables

Patch test frequency data have been extensively published by research groups, such as the International Contact Dermatitis Research Group, North American Contact Dermatitis Group, Dermato-Allergology Study and Research Group, and European Environmental Contact Dermatitis Research Group. As this knowledge accumulation is widely applied in clinical and public health settings, we describe confounding factors to consider when using such data for medical policy considerations. These concepts can also be used in individual reports of new allergens or series of cases. Some of these confounders may have been reported in current literature (until October 2020), whereas others have not been mentioned/considered in most group publications.

Pyrethrum Allergic Contact Dermatitis in Humans—Real?, Common?, or Not Documented?: An Evidence-Based Approach

Pyrethrum has been reported to produce allergic contact dermatitis in humans. Moreover, it has been speculated that cross reactions occur in ragweed-sensitized people. This review presents the botany, contemporary chemistry, and case reports of alleged allergic contact dermatitis. Our interpretation suggests that the evidence presented in literature does not show that allergic contact dermatitis results from exposure to pyrethrum. Similarly, the data do not suggest cross reactions in ragweed-sensitized people. Changes in the chemical composition of the refined pyrethrins suggest the putative sensitizer is present at a lower level in today's refined extracts than in ground pyrethrum flowers or the extracts used earlier.

Mystery of the disappearing allergen: published allergens rarely seen again

Patch testing is an important tool in the diagnosis of allergic contact dermatitis. Although this technique can be accurate, occasionally the results may be inconclusive. A previously positive result to an allergen may become negative upon repeat testing, and this may complicate the process of achieving a definitive diagnosis. There are some potential explanations for such inconsistencies, including the Excited Skin Syndrome, irritant reactions, a need to repeat the diagnostic algorithm, "rogue" reactions, and "contact allergy." These explanations should be taken into account when interpreting these results. However, further knowledge is needed to solve the mystery of an allergen that subsequently disappears.

In pursuit of defining clinical relevance of positive patch tests results

According to the current classification of clinical relevance of the positive patch test reactions, the positive results of patients who are allergic to various allergens that are not responsible for the present dermatitis do not fit into the category of "relevant to present dermatitis" but should be defined as "relevant to a preceding bout of dermatitis." This seems to us inappropriate and misleading because reexposure to the sensitizing agent would quickly revert their reaction to "relevant to present dermatitis." We suggest an alternative possibility to the current division of the various types of clinical relevance, namely, "relevance to a present allergy other than the presenting dermatitis."

Correlations of patch test reactivity and the repeated open application test (ROAT)/provocative use test (PUT)

The clinical relevance of patch test reactions is often difficult to determine. Use tests have been developed to further evaluate the significance of patch test results. We review studies that have defined correlations between the threshold concentrations at patch testing and the outcome of use tests for particular chemical allergens. Results of patch testing with serial dilutions of colophony, cinnamic aldehyde, and isoeugenol have shown concordance with the outcome of use tests. On the other hand, poor correlations between patch test reactivity and the use test were demonstrated in another study on isoeugenol and on studies on hydroxycitronellal, formaldehyde and chromium. These studies shed light on some factors that may influence the outcome of use tests. Individual factors such as patch test sensitivity, regional variations in reactivity and percutaneous penetration appear to play significant roles. Exposure dose, length of time of exposure, and other factors yet to be determined also affect degree of reactivity. Because patients with low thresholds in serial dilution patch testing are known to react to lower concentrations of products at use testing, results of these studies may be used to help identify subjects with a high risk of developing clinical disease. From the public health standpoint, data obtained may be used as a guide in limiting exposure concentrations in consumer products.

Allergic dermatoses

Defining "allergy" and elucidating the immunopathology of what is too often described as allergic rashes is the objective of this article. The differentiation of inflammatory reactions, which at times is indistinguishable from the immunologic dermatoses is outlined. A rationale plan for management, with indications warranting referral to "the specialist" are suggested.

1,2-Benzisothiazolin-3-one (Proxel): irritant or allergen? A clinical study and literature review

The isothiazolinone, 1,2-benzisothiazolin-3-one (Proxel), is a popular preservative, as well as a skin sensitizer and irritant. Patch test studies have been performed with different concentrations and vehicles. The current suggested patch test concentration is 0.1% BIT in petrolatum (pet). This article evaluates the effects of patch testing at this concentration and reviews the current literature. An irritancy patch test was performed on 56 controls, using BIT in concentrations of 0.002% and 0.05% in aqueous dipropylene glycol (Proxel GXL) and 0.1% in pet. 10 had positive readings at 4 days with 0.1% BIT in petrolatum, 9 of which were negative at retest. 0.1% BIT is, therefore, irritant and not a suitable concentration for patch testing. Literature review revealed 15 patch test studies, with varying testing techniques. Additional studies with adequate controls and experimental tests should be invaluable in furthering our insight into BIT sensitization and irritation.

Contact dermatitis

LEARNING OBJECTIVES

Reading this article will reinforce the reader's knowledge of the definition, pathophysiology, differential diagnosis, evaluation, and management of the most common of all the "eczemas," contact dermatitis, which can have an allergic and/or an irritant pathogenesis.

DATA SOURCES

Relevant articles and current texts on contact dermatitis were referenced and reviewed. The personal experiences of the authors in an Environmental Medicine Clinic, their private practices, and their teaching of residents and other physicians were evaluated. A MEDLINE database using subject keywords was searched from 1986 to date.

STUDY SELECTION

Book chapters, pertinent articles, data source abstracts, guidelines for the management of contact dermatitis set by the American Academy of Dermatology, and the American Contact Dermatitis Society were critiqued.

RESULTS

The recent elucidation of the pathoimmunology of contact dermatitis is concisely reviewed, highlighting its clinical implications. The protean clinical presentations of contact dermatitis, both "allergic" and "irritant" type are cited. The signs and symptoms warranting the search for a contactant are outlined. The most likely regional contactants are listed, but the need to reference a more complete textbook is often required. That patch testing is the gold standard to identify an allergenic agent causing allergic contact dermatitis is stressed. While the "who" and "when" to patch test is amply described, a cookbook "how" to patch test has been omitted in order to emphasize the importance of "hands on" experience for such testing. The advantages and limitations of the commercially available standard patch tests (Hermal, and T.R.U.E.) are described, plus the sources for "nonstandard" patch tests is made available. Therapeutic modalities, topical and systemic, for management of the uncomfortable patient are outlined.

CONCLUSION

The physician who manages a patient with an "eczematous" rash must be aware of the complete differential diagnosis of that clinical presentation. Suspicion that a "contactant" is the cause must have high priority, especially when the rash is persistent, and fails to respond to "appropriate" therapy. The value of a skin biopsy is limited to confirming its eczematous (spongiotic) nature and ruling out other diseases. Appreciating the paradox of patch testing, namely the deceptive simplicity of application versus the required expertise for interpretation and recognition of clinical significance, is the key to the proper management of the patient with contact dermatitis.

Supplemental tests in the evaluation of occupational hand dermatitis in soldiers

BACKGROUND

Hand dermatitis in soldiers is a considerable problem. The purpose of the study was to evaluate appropriate screening tests to improve the diagnosis of hand dermatitis in soldiers.

MATERIALS AND METHODS

A group of 111 soldiers with occupational dermatitis from contact with fuels and oils underwent "tailored patch tests" with allergens relevant to their field of work and their environment. The control group consisted of 24 soldiers with various jobs similar to those of civilian life, who had not been exposed to oils and fuels. Seventy-three civilian patients, attending the clinic for patch testing, were also included. Twenty soldiers, who had a history of intensive contact with oil and fuels, but no contact dermatitis, and who were admitted because of various skin diseases (fungal infections, acne, etc.) also underwent the supplemental testing and served as an additional control group.

RESULTS

Of the soldiers, 31 (29%) showed one or more positive skin tests of the oil series and 30 patients of this group one or more positive reactions to the standard patch tests trays. No patient of the control groups had a positive test to the oil series.

CONCLUSIONS

Our results show the value of the supplementary tests as a first-step screening test for detection of oil allergy in soldiers and automobile-mechanics or in workers handling other gasoline- or diesel-powered engineering equipment. The test method appears to be practical, easy to perform, reliable and giving clear and accurate results, with a negligible rate of false positive reactions.